Pneumatic control for air supplied to a stoker



Feb. 22, 1938. L, R, TEEPLE 2,108,873

PNEUMATIC CONTROL FOR AIR SUPPLIED TO A STOKER Filed July 17, 1934 2 Sheets-Sheet l fIIIIIIIIIIIIIIIII'I'I //\/4/5/\/ 777 L.. Q. TEEPLE' )4 TTUFQNE L. R. TEEPLE Feb. 22, 1938.

PNEUMATIC CONTROL FOR AIR SUPPLIED TO A STOKER Filed July 17, 1934 2 Sheets-Sheet 2 3 //\/z/E/v7-UR L Q TEEPLE )WTU E 3 v Ill/11111714711114. Y s

Patented Feb. 22, 1938 UNITED STATES PNEUMATIC CONTROL FOR- AIR SUPPLIED TO A STOKER Lawrence R. 'Teeple, Portland, Oreg.

Application July 17, 1934; Serial No. 735,617

'1 Claims.

This invention relates generally to underfeed stokers, and particularly to a means for automatically controlling the amountoi air supplied to the combustion.

The main object of this invention is the provision of an exceedingly simple and efficient form of control for the air delivered by.the stoker to the combustion zone of a furnace.

The second object isto provide a control means to be efficient in its operation, devoid of complications and at the same time capable of providing any desired amount of lag between the commencement of fuel delivery and that of air delivery.

These, and other objects, will become more apparent from the specification following as illustrated in the accompanying drawings, in which Fig. 1 is a perspective view of an underfeed stoker equipped with my device.

Fig. 2 is a section taken along the line 2-2 in Fig. 1 showing the pilot damper partly open.

Fig. 3 is a section taken along the line 3--3 in Fig. 1 showing the butterfly damper partly open. Fig. 4 is a somewhat diagrammatic view showing the relation of the parts in detail with the distance between the elements greatly reduced; Fig. 5 illustrates the internal structure of the air valve mechanism showing a position which the parts. can assume under conditions different than those which are illlustrated in Fig. 4.

Similar numbers refer to similar parts throughout the several views. Referring in detail to the drawings, there is 5 shown an underfeed stoker including the fuel hopper ill, the fuel feeding tube II and retort l2, to .which fuel is delivered from the hopper I!) through the tube II by means of a motor [3 which operates a screw (not shown); within the 40 tube H. The motor l3 also operates a fan with- The piston 2lis operated by an eccentric 22 whichis supported by the compressor block 23. The eccentricv 22 acts'directly against a roller 24 which is carried'by-the' piston-2l. The spring 25 holds the roller 24 against the eccentric 22 and an adjustment is provided forthe spring 25 in the form of a set screw 26. Air is admitted to the compressor by the laterally extending pipe 21 which communicates with an air filter 28. 5 The discharge end of the cylinder 20 is closed by a bushing 29 which forms ahead therefor. Within the bushing 29 is disposed a ball check 30 which closes on the intake stroke of the compressor and forces the incoming air to be drawn 10 through the filter 28. The compressed air is dscharged through a pipe 3| into an oil filter 32 which may be of' any suitable type, preferably a simple container in which is disposed a.fabric covered cage through which the air 15 passes for the purpose of removing oil there-. from, from which it passes through a throttle valve 33 provided with an adjusting screw 34. The compressed air is then carried to the T fitting 35, one opening of which communicates 20 with the bel1ows 36 which is supported by. the

bracket 31 within the casing 38. The bellows 36 actuates a rack 38 which meshes with a pinion '40 secured on the shaft 4| of a butterfly damper i9 which can substantially close 25 seen that same is secured .to the shaft 44 on which is secured a slotted indicator plate 45 from which projects a pointer 46 which is disposed The members 45 and 41 are mounted within a 45} casing 50 which supports a pivot 5! on which are \pivotally mounted the spring-urged arm 52, one

end of which rides against the cam 41 and the other end of which is acted uponby a spring 53 which re-acts against a second arm 54 which en- 50 gages a grooved collar 55 on the stem 55 which carries an air valve disk 57. The disk 51 seats over the outlet 58 of an air line 59 which connects with the side outlet of the T fitting 35.

The air line 59 is provided with a valve 60 hav- 55 ing a relief opening Bl which is adjustably controlled by means of the set screw 62. It is necessary to provide an outlet opening 63 by means of which air can escape from the outlet '58 when the disk 51 is withdrawn therefrom.

The operation of the device is as follows: Assuming that the stoker motor [3 is started in response to any of the usual controls, the pilot damper I8 having been at rest and the butterfly damper l9 being closed (as shown in Fig. 4) as the compressor I1 is operated and pressure builds up in the fitting 35 the bellows 36 becomes distended, moving the rack 38 and opening the butterfly damper l8, and the pilot dampplained.

As the pilot damper l8 continues to rise, un-

3 der the increasing flow of air permitted by the gradually opening butterfly damper I8, the cam 41 is carried with it-that is, the end 49, whose position can be regulated by the screw 48, desc'ends to a point which will permit the end of the arm 52 to move, under the influence of the spring 52A, and, through the arm 54, open the outlet 58.

While the compressor I1 is suiflciently large to overcome the leak at the outlet ii to the extent of operating the bellows 36, it is not able to do so when the outlet 58 is open, as stated, causing the butterfly damper l8 to be moved in a closing direction, under the influence of the spring 42, until the butterfly [9 reduces the air flow sumcientlyto bring about a sufficient drop of the damper I8, which will cause the cam 41 to again close the outlet 58.

*It can be seen from the foregoing that there is, produced by this arrangement a balanced conditionthat is, the attendant merely sets the flow falls below a predetermined minimum the' outlet 58 will be closed, causing the damper iii to be moved toward an opening position.

It might seem that this would bring about a rapid and continuous adjustment of the setting of the butterfly damper, but such is not the case in actual practice since the action is by no means instantaneous, the adjustments being slow and positive.

The purpose of the relief opening 8| which, as

stated, is not large enough to prevent the functioning of the bellows 38, is to gradually relieve the pressure from the line 58 whenever the air flow through the duct l5 stops completely, due to a stoker shut-down and the damper I8 is in the position of rest (as shown in Fig. 4).

Unless this relief opening 6| was present, or there was not enough natural leakage in the system, then the butterfly damper I! could remain in a partially open position during the shutdown so' that the next time the stoker was operated air would immediately pass the butterfly I9 and open the damper l8, producing an undesirable result, namely the delivery of air simultaneously with the delivery of fuel, causing the the pressure within the bellows 38, but the rate of air flow thereto.

I claim:

1. A pneumatic control for air supply to a stoker consisting of an air duct having a pilot damper mounted therein whose position is responsive to the flow of air through said duct, a control damper within said duct for controlling the flow of air therethrough, a pneumatic ac tuator for said control damper, an air supply controlled by the operation of said stoker for operating said damper actuator, and. a cam operated valve actuated by said pilot damper for controlling the pressure of air in said damper actuator.

2. The device described in claim 1, includingmeans for relieving the air pressure from the damper actuator when the pilot damper is at a position of rest.

3. A device of the class described, the combination of a fan, a motor for driving said fan, an air duct conveying air delivered by said fan, a pilot'damper within said duct actuated by air passing therethrough, an adjustable cam actuated by said pilot damper, an air valve operated by said cam, a control damper mounted in said duct for controlling the flow of air therethrough, a rack and pinion for operating said control damper, an air operated actuator for said rack controlled by said air valve, an air'compressor operated by said motor for delivering air under pressure to said actuator, said air valve constituting a means for relieving the pressure from said actuator when said .pilot damper is raised above a predetermined position by an excessive flow of air through said duct.

'4. The devicedescribed in claim '3, together with a means for continuously relieving the pressure from said actuator at a rate intermediate the rate of delivery by said compressor and the rate of flow through said pilot damper-actuated,

air valve. 4 v

5. The device described in claim 1, together with means for regulating the amount of air which can be delivered by said compressor to said damper actuator.

6. A pneumatic control for air supplied to stokers comprising an air duct having a butterfiy damper for regulating the amount of -air flowing through said duct, a pilot damper which is free to swing in said duct under the influence of air passing said. butterfly damper, a pneumatic actuator for opening said butterfly damper dur-- ing the operation of the stoker in connection with which this device is used, spring means for closing said butterfly damper in opposition to said pneumatic actuator, a source of compressed air connected to said actuator by means of a pipe, an air valve communicating withsaid pipe between said butterfly actuator and its source of air supply, means operated by said pilot damper for opening said air valve during the passage of an excessive amount of air through said ductand closing said air valve during the passage of a. quantity of air which is less than a predetermined minimum, a, throttle valve betweenthe source of air supply and said actuator for retarding the opening of said butterfly damper for a predetermined period after the commencement of air delivery'to said butterfly actuator.

7. In a. stoker the combination of an air supply duct having a fan for supplying combustion air thereto, a pilot damper in said duct responsive to the flow of air therethrough, a control damper within said duct for controlling the'flow of air therethrough, a pneumatic actuator for said control damper, means for delivering air to said actuator when said tan is operating, an air valve actuated by said pilot damper for releasing air through said actuator when the velocity of the air exceeds a chosen value, and means for bleeding air from said actuator to permit the control damper to close upon cessation of air flow to the actuator.

LAWRENCE R. 'I'EEPIE. 

